1. Technical Field
The present invention is related to producing analgesia or reducing pain by implantation of cellular material in the central nervous system (CNS) of a host susceptible to pain sensation. More particularly, the present invention is related to the implantation of isolated chromaffin cells or adrenal medullary tissue in the brain stem or spinal cord for producing analgesia when the implanted tissue or cell is induced to release nociceptor interacting substances.
2. State of the Art
Reports of successful implantation of nonhomologous neural tissue to the central nervous system without immunological rejection have been known and these reports
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have created interest in the potential of such transplants for restoring functional deficits. Improvements in reproductive behavior, cognition and motor behavior in lesioned animals have been reported following the implantation of appropriate fetal neuronal tissue. Implants of adrenal chromaffin cells have been shown to survive for long periods of time when transplanted into the central nervous system (Perlow et al., 1980, Proc. Natl. Acad. Sci. 77:5278-5281). Recently, adrenal medullary homografts have been implanted in the striatum of human Parkinson patients with encouraging results (Backlund et al., 1985, J. Neurosurg. 62:169-173). However, modulation of pain sensitivity by implants of living cells or tissue in the CNS has not heretofore been attempted. Since pain is not necessarily the result of damaged neuronal tissue, it is essential that the function of neural implants in intact, non-lesioned systems be assessed when determining pain sensitivity.